In this picture a galactic cluster, about five billion light-years away, produces a tremendous gravitational field that “bends” light around it. This lens produces multiple copies of a blue galaxy about twice as distant. Four images are visible in a circle surrounding the lens; a fifth is visible near the centre of the picture.

Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC96-10)

Galactic cluster of star cluster M35 and NGC2158.

iStockphoto/Thinkstock

Open cluster NGC 290, as seen by the Hubble Space Telescope.

European Space Agency and NASA

NGC 1508, a poor open cluster.

Courtesy of Lick Observatory, University of California

NGC 6705, a rich open cluster.

Courtesy of Lick Observatory, University of California

Distant galactic cluster, as observed by the Hubble Space Telescope.

This group consists mainly of irregular galaxies; its red colour is a product of red shift.

Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PR98-27b)

Distant galactic cluster, as observed by the Hubble Space Telescope.

This cluster is over seven billion light-years from Earth and provides an image of the universe in its youth. The colour of the galaxies is a product of red shift.

Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PR98-27)

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either of two general types of stellar assemblages held together by the mutual gravitational attraction of its members, which are physically related through common origin. The two types are open (formerly called galactic) clusters and globular clusters.

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